1. Field of the Invention
The present invention is directed to a method and apparatus for controlling axes of motion in automated or semi-automated machinery.
2. Discussion of Related Art
In a typical surface-mount circuit board manufacturing operation, a stencil printer is used to print solder paste onto a printed circuit board. A circuit board, broadly referred to as an electronic substrate, having a pattern of pads or some other conductive surface onto which solder paste will be deposited, is automatically fed into the stencil printer. One or more small holes or marks on the circuit board, called fiducials, is used to properly align the circuit board with the stencil or screen of the stencil printer prior to the printing of solder paste onto the circuit board. Once a circuit board has been properly aligned with the stencil in the printer, the circuit board is raised to the stencil by a substrate support, e.g., a table having pins, or a flexible support and fixed with respect to the stencil. Solder paste is then dispensed onto the stencil, and a wiper blade or squeegee traverses the stencil to force the solder paste through apertures formed in the stencil and onto the board. As the squeegee is moved across the stencil, the solder paste tends to roll in front of the blade, which desirably causes mixing and shearing of the solder paste so as to attain a desired viscosity to facilitate filling of the apertures in the screen or stencil. The solder paste is typically dispensed onto the stencil from a standard cartridge. After the print operation, the board is then released, lowered away from the stencil, and transported to another station within the printed circuit board fabrication line.
The stencil printers described above may typically be used in an electronics manufacturing facility in an automated assembly line with other equipment used to manufacture the circuit boards. The other equipment in-line with the stencil printers may include, for example, pick and place machines which place components on circuit boards, dispensing systems which are used for dispensing metered amounts of liquid or paste for a variety of applications, reflow ovens that are used to cure materials dispensed onto the circuit boards, and conveyors that may move circuit boards or other parts from one manufacturing station to another. These and many other types of automated or semi-automated machinery, use motors to provide movement of a variety of parts along different axes of motion. For example, in the stencil printers, motors may be used to move the squeegees and to move the circuit boards. In these and similar systems, a plurality of motors is generally required, one motor for each axis of motion (e.g., the x-axis, y-axis and z-axis), to provide desired motion along multiple axes. In conventional systems, a dedicated driver amplifier is required for each motor, and in addition, tuning parameters of the motors can be set for only one axis at a time.